<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>为什么div多层可以被选取到</title>
</head>

<body>
    <div>
        <div>
            demo
        </div>
    </div>
</body>
<script>
 let div= document.querySelector('div');
 console.log(div);
</script>    
</html>